Design and application of an oligonucleotide microarray (nifH-phylochip) for nifH gene-based detection of nitrogen-fixing prokaryotes

Biological nitrogen fixation, the enzymatic reduction of N:sub:2:/sub: to ammonium, is anexclusively prokaryotic process which is crucial to balance the global nitrogen cycle.The key enzyme of this process -- nitrogenase -- has been highly conserved throughevolution. Transcription of one of the nitrogenase structural genes, nifH, provides apractical genetic marker for nitrogen fixing conditions and diazotrophic activities, as itis not constitutively expressed and is regulated in response to factors that controlnitrogen fixation. Our study focused on developing an oligonucleotide microarray(nifH-phylochip) for the nifH gene-based detection of nitrogen-fixing prokaryotes andapplying it to assess the functional diversity of diazotrophic prokaryotes within thecontext of complex environmental samples.